1. Field of the Invention
The present invention generally relates to an aluminum alloy used as a material for high strength parts. The present invention also pertains to various members or parts made of such an alloy as, for example, forged parts, fastening parts, in particular to aluminum alloy based high strength bolts of high strength above 450 Mpa.
2. Background Information
In recent years, due to an increasing need for improving fuel efficiency of automobiles, a reduction in weight of parts is required to improve fuel efficiency. As a concrete measure of lightweight, it is effective to replace steel parts by light alloy such as aluminum alloy or magnesium alloy. For example, when an automotive engine or transmission case should be constructed by using a magnesium alloy to achieve lightweight, it is desirable to change fastening parts (bolts, for example) made of steel for their fastening for aluminum alloy based parts in view of prevention of electrolytic corrosion and weight reduction.
As the fasteners made of aluminum alloy such as these, a high strength aluminum alloy screw is known which is made of forged material of 6000 series aluminum alloy (Al—Mg—Si base), (see e.g., Japanese Patent No. 3,939,414).